Typical triterpenes are terpenes consisting of six isoprene units and typically have the molecular formula C30H48. Pentacyclic triterpenes can be classified into lupane, oleanane, or ursane groups. Animals, plants, and fungi, create triterpenes, like, squalene, ambrein and ganoderic acid.
The steroidal skeleton depicted in FIG. 2 gives the generic structure for sterols and triterpenes. Most phytosterols (plant sterols) are tetracyclic, as in the picture. Many triterpenes can also be pentacyclic. There is generally an OH-group in position 3. This OH-group can be esterified or free, hence the differentiation between sterol esters and free sterols. The methyl groups in position 4 distinguish triterpenes from other steroidal compounds. Both methyl groups are present in triterpenes, one methyl group is present in methylsterols and no methyl groups are found in the desmethylsterols. The typical plant and animal sterols are desmethylsterols and these are colloquially known as phyto- and zoo-sterols. The most common phytosterol is beta-sitosterol. A huge variety of structures are known, defining different classes of triterpenoids. Pentacyclic structures usually have higher melting points compared to the tetracyclic steroids and are more difficult to isolate from the plant materials.
In shea butter, several classes of triterpenoids are known, including lupanes, ursanes and oleananes. Each of these classes can be represented by several individual triterpene alcohols. The triterpene alcohols in shea butter are usually esterified to cinnamic, acetic and other carboxylic acids.
There are today three main commercial routes to enrich unsaponifiable matter such as triterpene esters from vegetable oils; via molecular distillation, via solvent fractionation and via hydrolysation.
Fractionation is a method to separate materials based on the melting point, where for example, the high-melting triglycerides are made to crystallize, leaving the unsaponifiable matter dissolved in the liquid phase. Without hydrogenation the maximum concentration obtained is below 25 wt % of unsaponifiable content. Hydrogenation followed by interesterification and repeated fractionations can give a higher concentration unsaponifiable matter, up to 70 wt %. Hydrogenation and interesterification will lead to chemical modification of the unsaponifiable matter, for example changing the proportions of cinnamic, acetic and fatty acid esters of triterpene alcohols found in shea butter. The processes used are also very complex and using large capacity. At least for some productcategories the hydrogenation itself is less desirable from a consumer point of view.
Molecular distillation (also named short path distillation) is a method using extremely low pressure, in the order of magnitude around 0.001 Pa. The temperature in commercial units hardly goes above 260° C. The method uses the boiling point to separate different chemical species from each other. The limitations are that at lowest available pressure the boiling points must be lower than 260° C. for parts or the whole of the material and there must be a difference in boiling point between the molecules that are to be separated. In the case of shea butter, the triterpene acetates have the lowest boiling point, followed by diacylglycerides and almost at the same temperature, triterpene cinnamates, which makes it difficult to completely separate the acylglycerides from the triterpene esters.
Hydrolysation can be performed by adding alkali/water or water/high temperature to hydrolyse the ester bonds. Here also the triterpene ester bonds are also potentially broken, producing free triterpene alcohols with low solubility and high melting points.
WO 97/21697, U.S. Pat. No. 5,627,289, U.S. Pat. No. 4,451,564, U.S. Pat. No. 4,148,810 all disclose methods to produce concentrates of unsaponifiable matter where it is necessary to remove about 98% oil by distillation at about 220-260° C. and 3-20 mbar pressure. All those documents describe procedures where the starting material is a distillate from deacidification of vegetable oils. Thus the mixture used as a starting material has been subjected to distillation in the above disclosures, which does not preserve the natural composition of the triterpene esters. It also adds to the complexity and cost in the above disclosed processes.
US20110220483 discloses a process to produce sterol alcohols and triterpene alcohols from a distillate fraction. Enrichment of esters of triterpenes is not disclosed.
US20110220483 discloses that the ingoing material is in fact the distillation fraction when deodorising an oil. The process is a high temperature process, typically 200 to 250° C. under low pressure conditions, typically 1-50 mbar. Sparge steam is often used to enable all volatile products to be removed in the distillation phase. Here free sterols alcohols are distilled off with a number of other molecules such as free fatty acids, triglycerides, hydrocarbons, squalanes and impurities. Peroxides and aldehydes follow with the distillation phase. This is the starting material. In the distillation fraction very few triterpene esters are found as they are kept in the residual.
After that in order to enrich the alcohols of the sterols it has to go through a number of process steps, which all require very different design, such being able to handle both very low pressure and very high pressure, high temperatures and low temperatures. Except for the complex production method itself, the method will not result in native sterol esters, but alcohols of sterols and triterepenes without any acid bound to them. Free sterols and triterpene alcohols have a very much higher melting point than in the form of an ester, which make them difficult to use in a number of different applications.
US 20020058827 discloses using a distillation fraction as the starting material. More than 95% of the sterols in fact is in form of a sterol alcohol and less is in form of sterol ester. The distillate is then reacted with glycerol at a very high temperature, 215° C., which is not a gentle and energy efficient method.
In summary US 20020058827 and US20110220483 do not disclose a process where the main form of sterols are in the form of an ester, instead sterol alcohols are enriched. The ratio of sterol esters/sterol alcohol is less than 0.05.
In view of the above described drawbacks there is room for an improved method to enrich triterpene esters.